Fuse for use with liquid-oxygen explosives



May 26, 1%25.

Q. MOTT ET AL FUSE FOR USEWITH LIQUID'OXYGEN EXPLOSIVES Filed April 14, 1924 A 7 m W? W m fiwm 5 m. fi/fl W Na m mar T flag A, 2 Afr 5 Patented May 26, 1925.

rs aqacis CHESTER MOTT, LUTHER ETBEDORTHA,

AND ROBERT J. KILLGORE, OF DENVER,

. COLORADO, ASSIGNORS', BY MESNE ASSIGNMENTS, TO PUROX COMPANY, OF DEN- VER, COLORADO, A CORPORATION OF COLORADO.

FUSE FOR USE WITH LIQUID-OXYGEN EXPLOSIVES.

Application filed April 14, 1924. Serial No. 706,271;

To all whom z'tmag concern:

Be it known that we, CHESTER Mo'r'r, LUTHER E. BEDORTHA, and ROBERT J. KILL- GORE, citizens of the United States, residing in the city and county of Denver, State of Colorado, have invented a new and useful Fusefor Use with Liquid-Oxygen Explosives, of which the following is a specification.-

7 Our invention relates to the art of blasting and more particularly tothe fusesused in that art. It is commonpractice, especiallyin metal mines, to blast down the rock by means of a plurality of simultaneous or dependent explosions. Holes aredrilled in the rock to be blasted in a certain relationship with each other, and one or more ex plosive cartridges are placed in each hole, the cartridges in each hole being detonated simultaneously and the cartridges in the different holes being usually detonated in a certain order with a short time interval between. This is to allow certain of the holes to break the rock first, thus breaking away the entire structure progressively. This progressive method is generally called blasting with dependent holes.

To-be successful, blasting by the use of dependent holes requires a very certain timing of the different holes, since the last holes to go under correct timing are charged only to a degree to break away the rock remaining after the first holes have been exploded. If for any reason the holes do not fire in their proper order, and the rock is not broken as planned, certain ofthe holes are ineffective and the advantage of progressive and dependent blasting is destroyed. It is therefore quite essential that any type of fuse used must have a constant known burning rate under all conditions in which it is used. This is particularlytrue when using liquid oxygen explosive, since the effect of. such explosive is to cool the fuse and slow down its burning rate. In blasting with liquid oxygen explosive a prepared cartridge formed of absorbent carbonaceous'material is soaked in liquid oxygen, several of the cartridges being placed in each hole which it is desired to blast. It is common practice to use a fuse which passes down the hole alongside the cartridge to a point near the bottom of the hole. where it explodes a detonator. It is very diflicult to make a fuse which will burn at a uniform rate which .will not occasionally side spit, or blow flame out of openings in the side of the fuse. It is necessary, if the burning rate is to be uniform, that the gas pressure built up inside the fuse shall be uniform. If the Walls of the fuse are made impervious to gas, the burning of the fuse tends to build up the gas pressure and to accelerate the rate of burning. If, on the other hand, the walls of the fuse are made sufficiently porous to allow the gas to escape, there is considerable danger that this escaping gas, or incandescent particles of burning powder, will prematurely ignite the cartridges, especially where the fuse passes down along the side of the. hole in close proximity to such cartridges. Many types of explosives will burn quietly even in an enclosed space without detonation. In such event the explosive is, of course, ineffective and is simply wasted in producing gases which are generally objectionable. It is an objectof our invention to provide a fuse which will have a uniform burning rate and which may be depended upon not to side spit-or ignite cartridges of liquid oxygen explosive alongside of which it may be placed.

Further objects and advantages will be made evident hereinafter.

Referring to the drawing which is for illustrative purposes only,

Fig. 1 is a section through a typical drill hole showing the method of charging it.

Fig. 2 is a view of a fuse adapted to be used in the hole shown in Fig. 1.

Fig. 3 is a View of the detonator.

In the form of the invention illustrated, 11 is the face at which the mining operations are carried on and 12 is a hole drilled through this face into the formations beyond. Situated in the hole 12 are a pluiality of liquid oxygen cartridges 13 and situated between two of the cartridges 13 is a detonator 14. this detonator being of standard form and consisting of a body of very high explosive suitably incased. Extending downwardly to the detonator 14 is a fuse 20, this fuse extending out from the hole and having a projecting end 21 to which may be connected bus fuses so that a plurality of holes can be exploded in any desired order. v

The fuse 20 consists of a highly coinbustible core 30 surrounded by a filler "31 and a braid 32. Wrapped loosely about the braid 32 is an aluminum foil sheath 33 and over the aluminum sheath 33 is a broad cover 34. The aluminum sheath 33 may be. formed of thin and relatively narrow tape wound around the fuse, as shown, or it may consist of absorbent gauze having small openings therebetween. In blasting with liquid oxygen explosive, the cartridges have a very high heat absorbing capacity and they liberate oxygen at very low temperature which almost immediately cools the wall of the hole and everything in it. The aluminum sheath 33 is therefore immediately lowered in temperature. The filler 31 and the wall 32, as well as the braid cover 34, are made very porous so that gases can readily escape during the burning of the fuse, these gases passing between the turns of the aluminum tape 33 or through the meshes of the gauze which may be substituted therefor. Since aluminum has a very high heat absorbing capacity, it immediately cools these gases to such a degree that side spitting is a practical impossibility. We have found in practice that a fuse of this type laid alongside of liquid oxygen cartridges does not ignite these cartridges,

the fuse burning through its entire length and exploding all'of the cartridges through the detonator 14. We have also found that a fuse made in this way of very loose texture will readily vent the gases as formed in the fuses and that an absolutely reliable fuse is produced, the rate of burning being substantially constant. This allows the operator to arrange his charges to explode in. any order with a reasonable certainty that they will explode in that order and that al of the charges will be effective.

l/Ve claim as our invention:

. 1. A fuse for use with liquid oxygen explosive comprising: a core containing combustible materials; and a heat absorbent sheathing over said core so applied that the gases of combustion can escape therethrough and'be. cooled thereby as they escape.

2. A'fuse for use with liquid oxygen explosive comprising: a core containing combustible materials; a heat absorbent sheathing over said core so applied that the gases of combustion can escape therethrough and be cooled thereby as they escape; and a cover loosely woven over said sheathing to act as a mechanical protection therefor.

A fuse for use with liquid oxygen explosive comprising: a core containing combustible materials; and a metallic sheathing over said core so applied that the gases of combustion can escape therethrough and be cooled thereby as they-escape. v

4. A fuse for use with liquid oxygen explosive comprising: a core containing combustible materials; a metallic sheathin over said core so applied that the gases 0 combustion can escape therethrough and be cooled thereby as they escape; and a cover loosely woven over said sheathing to act as a mechanical protection therefor.-

5. In a fuse of the character described, the combination of: a core containing combustible materials; and a metallic sheathing over said core soapplied in loose arrangement that the side spitting of the burning core is prevented and the gases therefrom may escape through the interstices of said metallic sheathing.

6. In a fuse of the character described, the combination of: a core containing combustible materials; a metallic sheathing over said core so applied in loose arrangement that the side spitting of the burning core is prevented and the gases therefrom may escape through the interstices of said metallic sheathing; and a cover woven over said sheathing to act as a mechanical protection therefor.

In testimony whereof, we" have hereunto set our hands in the city and county of Denver, State of Colorado, this 27th day of March, 1924.

CHESTER MOTT. LUTHER E. BEDORTHA. ROBERT J. KILLGORE. 

